ecmascript/javascript version

 

Overview

In Javascript 5th edition of the spec, a lot of new functionality has been introduced (no threads or classes yet though, bummer, but class and import and export are future reserved words). the way to detect that new functionality is through the new function Array().indexOf(n): that means you won't find it in javascript 3rd edition, the previous edition of the standard, which is what is currently what is used in ie8 10/27/2010. Sorry, IE9 isn't for XP users (thanks microsoft for the push towards firefox).

Javascript 5th Edition?

Result for Array(1,2,4,5,10,20).indexOf(10):